Good Medium to Small Reptile or Amphibian Pets

Recently, I purchased a 20 Gal tank for my fish, only to realize that it can't hold water. I can't return it, so I am trying to find a few good animals to keep in it. Any ideas or thoughts would be great. I'm fairly experienced in caring for fish, but have never had any reptiles or amphibians. The tank can probably hold water about a quarter of the way full, and is 18 inches long, and 12 inch deep and wide.

One leopard gecko can fit comfortably in a 20gal. They're good beginner pets- small, easy to feed, come in a ton of different colors and patterns, and easily tamable. My only thing is I would recommend getting one from a breeder or reptile expo instead of Petsmart or any of the big chains. They often have sick/unhealthy animals. Just make sure you do your research because some breeders really aren't much better! An expo would probably be your best bet.

I would recommend a leopard gecko, or a small group of anoles and/or long-tailed lizards. I am a pet care specialist at PetSmart and also have multiple certifications. PetSmart takes very good care of our animals and we do not purchase our pets from large breeders/warehouse breeders. At PetSmart our animals go to Banfield, our veterinary team as soon as the slightest bit of sickness or injury is found.